Materials Science Multiple Choice Questions & Answers on “Eutectoid and Peritectic Reactions”.
1. On heating, one solid phase results in another solid phase and a liquid phase during __________ reaction.
a) Eutectoid
b) Peritectic
c) Eutectic
d) Peritectoid
Answer: b
Clarification: Peritectic reaction is the reaction in which one solid phase converts into another solid phase and liquid at a constant temperature.
2. A first solid phase results in a second solid phase another third solid phase on cooling during __________ reaction.
a) Eutectoid
b) Peritectic
c) Eutectic
d) Peritectoid
Answer: a
Clarification: Eutectoid reaction is a reaction in which one phase is converted into two different phases at a constant temperature. Iron-carbon diagram is one of the examples of the Eutectoid phase diagram.
3. A first solid phase results in a second solid plus another third solid phase upon heating during __________ reaction.
a) Eutectoid
b) Peritectic
c) Eutectic
d) Peritectoid
Answer: d
Clarification: Here only the solid phase is involved and the product is also solid.
4. Which phase will crystallize first just below the liquidus line?
a) α phase
b) β phase
c) (L+α) phase
d) (L+β) phase
Answer: a
Clarification: The α phase will crystallize first because it is just below the liquidus line.
5. At what temperature, all liquid and α will convert to β?
a) Eutectic temperature
b) Peritectic temperature
c) Eutectoid temperature
d) Peritectoid temperature
Answer: b
Clarification: L + α → β, the above reaction is peritectic and takes place at peritectic temperature.
6. Any composition left and right of P will generate ___________
a) Excess of liquid and α
b) Excess of α and liquid
c) Excess of liquid and β
d) Excess of β and liquid
Answer: b
Clarification: Any composition left of P will generate excess α and similarly right of P will give rise to an excess amount of liquid.
7. Which of the following are Peritectic systems?
a) Pt – Ag
b) Ni – Re
c) Ni – Re, Fe – Ge, Sn-Sb
d) Pt – Ag, Ni – Re, Fe – Ge, Sn-Sb
Answer: d
Clarification: Peritectic systems – Pt – Ag, Ni – Re, Fe – Ge, Sn-Sb (babbit).
8. What is the eutectoid structure of Iron?
a) Cementite
b) Ferrite
c) Pearlite
d) Austentite
Answer: c
Clarification: It is important to be known that pearlite isn’t a phase, but a mixture of two phases: ferrite and cementite.
9. What is the maximum %C by weight in hypo-eutectoid steels?
a) 0.5%
b) 0.7%
c) 0.8%
d) 1.2%
Answer: c
Clarification: Steels with less than 0.8% carbon are known as hypo-eutectoid steels. Its micro-structural components are α-ferrite and pearlite.
10. The phase above eutectoid temperature for carbon steels is known as _______
a) Cementite
b) Ferrite
c) Pearlite
d) Austentite
Answer: d
Clarification: In the Fe-C system, there is a eutectoid point at 0.8wt% C, and temp of 723°C. The phase just above the eutectoid temperature for carbon steels is known as austeniteor gamma.
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